Staging: wlan-ng: remove unused #include <version.h>

The file(s) below do not use LINUX_VERSION_CODE nor KERNEL_VERSION.
  drivers/staging/wlan-ng/p80211conv.c
  drivers/staging/wlan-ng/p80211req.c
  drivers/staging/wlan-ng/p80211wext.c
  drivers/staging/wlan-ng/prism2mgmt.c

This patch removes the said #include <version.h>.

Signed-off-by: Huang Weiyi <weiyi.huang@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>